1. Field of the Invention
The present invention relates to the packaging art, and, more particularly, to the art of reclosable plastic bags or packages having extruded zippers. In particular, the present invention relates to extruded zippers having two sets of mutually interlocking members separated by at least one compressible or partially collapsible member, the latter forming a watertight seal when the mutually interlocking members are closed.
2. Description of the Prior Art
Reclosable bags used, for example, for storing household foodstuffs are typically made of polyethylene. As shown in U.S. Pat. No. 3,416,199 to Imamura, which is commonly assigned with the present invention, a reclosable bag may be formed of two opposed walls and having a mouth equipped with fastener profiles. These profiles include a male profile attached to one wall and a female profile attached to the other wall. The profiles are shaped so that, when they are aligned and pressed together into an engaging relationship, they form a continuous closure for the bag. The bag may be opened by pulling the walls apart at the mouth, thereby separating the male and female profiles from one another.
The prior art is replete with different shapes and arrangements for the male and female profiles. In many cases, the profiles are designed to provide relatively high resistance to opening from inside the package, while rendering the package relatively easy to open from the outside.
Because the male and female profiles must be shaped so as to be readily interlocked with one another, they may not form an entirely airtight closure. For this reason, peel seals are used in the reclosable plastic packages used for the retail sale of foodstuffs to ensure that the packages remain hermetically sealed prior to sale. Moreover, the peel seals can also serve a tamper-evident function by whitening or otherwise discoloring when being opened, thereby providing a means by which a prospective purchaser could be alerted to the possibility that the package had been opened prior to purchase.
Following purchase, there may still be a need to form a hermetic seal after the initial opening of the package to preserve the freshness of any contents remaining in the package. The present invention is a watertight closure which provides such a seal.